1. Field of the Invention
This work was supported by the IT R&D program of MIC/IITA. [2006-S-059-01, ASON based Metro Photonic Cross-Connect Technology]
The present invention relates to an optical communication device, and more particularly, to an optical transceiver which can control optical output jitter and a method of controlling optical output jitter using the optical transceiver.
2. Description of the Related Art
An optical transceiver is a communication module which carries out optical-electric conversion and electric-optical conversion in an optical communication system. Due to increases in speed of the optical communication devices, optical transmission speed of the optical transceiver has increased to over 10 Gb/s, however, the size of the module has become smaller. Also, in order to increase price competitiveness, FR-4, which is generally used in existing materials having low permittivity, is used in a printed circuit board (PCB) used in the optical transceiver having the optical transmission speed of 10 Gb/s.
When a high-speed electrical signal having an optical transmission speed of 10 Gb/s is transmitted through FR-4, high-frequency components of the signal is significantly reduced due to dielectric loss of the FR-4. In addition, if an impedence matching among a package of a chip, a Packet Assembly/Disassembly (PAD), and a transmission line is not well accomplished, reflection of high-frequency component greatly occurs and thus causes jitter.
FIG. 1 is a graph illustrating attenuation of an electric signal S21 in a transmission line on a conventional PCB. It shows a transmission characteristic S21 when an electrical signal having the optical transmission speed of 10 Gb/s is transmitted via the transmission line of the PCB that is formed of FR-4. As shown in FIG. 1, high attenuation occurs for high-frequency component.
FIG. 2 is a block diagram of a conventional optical transceiver.
Referring to FIG. 2, when a conventional optical transceiver 50 is a XFP (10 Gb/s Small Form-factor Pluggable) transceiver, transmitted data TD+/− at the optical transmission speed of 10 Gb/s is input into the transceiver through a connector. Then, electric-optical conversion occurs, so that the transmitted data TD+/− is converted into an optical signal of 10 Gb/s in a Transmitter Optical Sub-Assembly (TOSA) 16 through a Clock and Data Recovery (CDR) unit 12 and a Laser Diode (LD) driver 14 and then the optical signal is transmitted through an optical fiber. Meanwhile, when the optical transceiver 50 is a 300-pin Multi-Source Agreement (MSA) transceiver, 600 Mb/s×16 streams of transmitted data TD+/− are input into of the transceiver through a connector. Then the transmitted data TD+/− is converted into an electric signal of 10 Gb/s in a serializer 12 and is converted into an optical signal through the LD driver 14 and an LD module 16.
In the case of the XFP transceiver, an optical signal is received as received data RD +/− through a Receiver Optical Sub-Assembly (ROSA) 22, a limiting amplifier (LIA), and a Clock and Data Recovery (CDR) 24. In the case of the 300-pin MSA transceiver, an optical signal is received as received data RD +/−through a Photo Diode (PD) 22 and a deserializer 24. A micro-controller 30 controls devices included in a transmission unit 10 and a receiving unit 20 of the optical transceiver 50.
Parts that perform such functions described above are connected with each other on the PCB so as to transmit signals and thus transmission lines that can transmit an electric signal having a optical transmission speed of 10 Gb/s should be precisely designed and manufactured, otherwise, an Inter-Symbol Interference (ISI) phenomenon is accumulated every time a high-frequency signal passes through the parts due to reflection and attenuation of the high-frequency signal and thus jitter is significantly increased in a final optical output stage. A characteristic of an optical output jitter is important among various characteristics of an optical transceiver which affect the performance of the optical transceiver and thus a PCB should be carefully designed and manufactured to allow the optical transceiver to be able to perform at optical transmission speeds of over 10 Gb/s.